1. Technical Field
The present invention relates to vibratory feeders or conveyors and, more particularly, to reversible or two-way vibratory feeders or conveyors.
2. Background Art
Two way vibratory feeders or conveyors have substantial applications in a variety of fields. One typical application is foundry applications. For example, castings may be delivered to the feeder at a location intermediate its ends and then the feeder is energized to feed the castings to one end or the other depending upon where it is desired to locate the castings. Typical two-way feeders include an elongated bed with an upwardly facing, generally horizontal conveying or feeding surface which terminated at opposite ends. The bed is supported on isolation springs adjacent the ends which in turn serve to mount the bed above the underlying terrain such as a floor in a factory building or the like.
Two motor and weight assemblies, which form vibration inducing systems, are secured to the bed generally centrally thereof. Each will typically include a squirrel cage motor having a rotary output shaft to which is secured an eccentrically mounted weight. Springs in the form of plastic or fiberglass slats connect each of the motors to the bed.
Each of the vibration inducing systems is canted at approximately 45 degrees to the bed but in directions oppositely of one another. When it is desired to feed in one direction, one of the vibration inducing systems is energized while the other remains quiescent. If the opposite direction of feeding is required, then the other vibration inducing system is energized while the first remains quiescent.
In many applications it is not unusual that there is a considerable disparity between the amounts of use of the two vibration inducing systems. If one system is used to the substantial exclusion of the other, so called "false Brinnelling" of the motor bearings on the unused systems will occur as a result of the vibration imparted to the bed by the first system. Lubricant may be squeezed out of the bearings as a result and when the system is finally energized, it may fail relatively quickly as a result of bearing failure.
Moreover, in foundry applications, the bed typically will be formed of metal to stand up to the continued poundings of castings. In a prior art system such as described, vertical acceleration of the feeding surface during operation will typically exceed that of gravity. As a result, after the surface has reached its highest point of movement in a cycle of vibration, it will then be accelerated downwardly more rapidly than a casting or the like conveyed by the feeder in responding to gravity. The casting will be temporarily suspended above the conveying surface but will eventually collide with it as movement of the surface begins to reverse while the casting is being moved downwardly under the influence of gravity. The result is a noise producing impact of the casting upon the metal of which the conveying surface is formed and the noise level will typically be undesirably high.
Still further, in applications requiring conveying of powders, the vertical acceleration of the feeding surface tends to fluff up the powder so that it acts as a fluidized bed on the conveyor surface. When that occurs, the powder is incapable of being conveyed.
Prior attempts to address such problems are disclosed in U.S. Pat. Nos. 3,746,149 and 5,713,457, which illustrate systems in which a single motor is used to impart vibration to a conveying surface so that it may convey in either of two directions. While the structure disclosed in U.S. Pat. No. 5,713,457 works well for its intended purpose, both of these structures, which impart a motion to the conveying surface which is substantially in the form of an elongated ellipse, involve varying degrees of complexity and associated costs. Further, these structures still impart some degree of vertical motion to the conveying surface and thereby still potentially can encounter noise problems as well as problems conveying powders such as discussed above.
It will also be appreciated that the provision of two vibration inducing systems in a single feeder or conveyor when only one is used at any given time adds considerably to the cost of the apparatus.
The present invention is directed toward overcoming one or more of the problems set forth above.